Kazemi Mohammad, Ghanbari Mohammad, Shirmohammadi Shervin
IEEE Trans Image Process. 2020 Mar 31. doi: 10.1109/TIP.2020.2984356.
In highly-interactive video streaming applications such as video conferencing, tele-presence, or tele-operation, retransmission is typically not used, due to the tight deadline of the application. In such cases, the lost or erroneous data must be concealed. While various error concealment techniques exist, there is no defined rule to compare their perceived quality. In this paper, the performance of 16 existing image and video quality metrics (PSNR, SSIM, VQM, etc.) evaluating errorconcealed video quality is studied. The encoded video is subjected to packet loss and the loss is concealed using various error concealment techniques. We show that the subjective quality of the video cannot be necessarily predicted from the visual quality of the error-concealed frame alone. We then apply the metrics to the error-concealed images/videos and evaluate their success in predicting the scores reported by human subjects. The errorconcealed videos are judged by image quality metrics applied on the lossy frame, or by video quality metrics applied on the video clip containing that lossy frame; this way, the impact of error propagation is also considered by the objective metrics. The measurement and comparison of the results show that, mostly though not always, measuring the objective quality of the video is a better way to judge the error concealment performance. Moreover, our experiments show that when the objective quality metrics are used for the assessment of the performance of an error concealment technique, they do not behave as they would for general quality assessment. In fact, some newly developed metrics show the correct decision only about 60% of the time, leading to an unacceptable error rate of as much as 40%. Our analysis shows which specific quality metrics are relatively more suitable for error-concealed videos.
在诸如视频会议、远程呈现或远程操作等高交互性视频流应用中，由于应用的严格时限要求，通常不使用重传。在这种情况下，必须对丢失或错误的数据进行掩盖。虽然存在各种错误掩盖技术，但尚无比较其感知质量的明确规则。本文研究了16种现有图像和视频质量指标（PSNR、SSIM、VQM等）评估错误掩盖视频质量的性能。对编码视频进行丢包处理，并使用各种错误掩盖技术对丢失的数据进行掩盖。我们表明，仅从错误掩盖帧的视觉质量不一定能预测视频的主观质量。然后，我们将这些指标应用于错误掩盖后的图像/视频，并评估它们在预测人类受试者报告的分数方面的成功率。通过应用于有损帧的图像质量指标或应用于包含该有损帧的视频片段的视频质量指标来判断错误掩盖后的视频；这样，客观指标也考虑了错误传播的影响。结果的测量和比较表明，虽然并非总是如此，但测量视频的客观质量是判断错误掩盖性能的更好方法。此外，我们的实验表明，当使用客观质量指标来评估错误掩盖技术的性能时，它们的表现与一般质量评估时不同。事实上，一些新开发的指标只有大约60%的时间能做出正确的判断，导致高达40%的不可接受错误率。我们的分析表明了哪些特定的质量指标相对更适合错误掩盖后的视频。
